Vehicle traction control and traction assist systems commonly employ two control modules: (1) a anti-skid brake system (ABS) module which controls the application of torque to the wheels from both the engine and the braking system, and (2) an electronic engine control (EEC) module which responds to commands from a variety of sources, including the ABS module, to control the amount of power produced by the engine. To achieve traction control, the ABS module receives a value from the EEC module indicating the estimated wheel torque, which the ABS module then uses to form and evaluate control commands sent to the EEC module and the braking system.
In prior systems, the EEC module produces the estimated wheel torque value by first calculating actual engine torque based on the current engine operating conditions, and then employs the resulting engine torque value in combination with vehicle status information (the current gear ratio and losses caused by other power consumers such as the air conditioner, etc.)
Comparisons of the actual measured wheel torque with the estimated wheel torque values produced by conventional methods has shown that these predicted torque values are prone to error because the mechanism for generating the estimated value does not take all inertial forces and other effects into account.
In co-pending application Ser. No. 08/524,274, assigned to the assignee of the present invention, which is incorporated herein by reference in its entirety, provides a means for calculating driveline inertia to improve traction control function. The present invention improves on these calculations by separating the inertia of the torque converter, shuffle mode dynamics and differential torque differences.